I’ve always felt that string plays best AFTER the first 15 - 20min of play. This allows the bounce and tension across the length of string to balance out.
I usually play a string for at least 15 hours before changing. After 10 years, I think I’ve only actually broken 6-7 strings. I change when I start to worry about them snapping (very frayed), or when they feel sticky (ie. the string is dirty, sticks to fingers and makes managing tension more difficult).
The exception to this is when playing fixed axle… Then I’ll change about every hour or so.